fix(windows): hide conhost window spawned with core sidecar (#731)

The core binary is a console-subsystem .exe so `openhuman core run`
works correctly in a terminal. When the GUI shell (which is built with
`windows_subsystem = "windows"`) spawns it as a child without the
`CREATE_NO_WINDOW` creation flag, Windows allocates a fresh conhost
window that pops up on top of the app.

Apply `CREATE_NO_WINDOW` (0x08000000) at every site where the GUI
launches a core subprocess:

- `core_process.rs`: both sidecar spawn paths (`CoreRunMode::InProcess`
  fallback and `CoreRunMode::ChildProcess`).
- `lib.rs`: the short-lived `run_core_cli` used by `service_*_direct`
  commands.

Non-Windows builds get a no-op helper, so the cross-platform call sites
stay identical. Stdout/stderr piping for log forwarding is unaffected.

app/src-tauri/src/core_process.rs

@@ -25,6 +25,21 @@ fn apply_core_color_env(cmd: &mut Command) {
     }
 }
 
+/// Hide the console window that Windows would otherwise allocate for the
+/// core sidecar. The core binary is a console-subsystem executable so that
+/// `openhuman core run` in a terminal behaves normally, but when the GUI
+/// shell spawns it as a child a stray conhost window pops up on top of the
+/// app. `CREATE_NO_WINDOW` suppresses that while leaving stdout/stderr
+/// piping intact for our log forwarding.
+#[cfg(windows)]
+fn apply_core_no_window(cmd: &mut Command) {
+    const CREATE_NO_WINDOW: u32 = 0x0800_0000;
+    cmd.creation_flags(CREATE_NO_WINDOW);
+}
+
+#[cfg(not(windows))]
+fn apply_core_no_window(_cmd: &mut Command) {}
+
 #[derive(Clone, Copy, Debug, Eq, PartialEq)]
 pub enum CoreRunMode {
     InProcess,
@@ -142,6 +157,7 @@ impl CoreProcessHandle {
                         cmd
                     };
                     apply_core_color_env(&mut cmd);
+                    apply_core_no_window(&mut cmd);
                     let child = cmd
                         .spawn()
                         .map_err(|e| format!("failed to spawn core process: {e}"))?;
@@ -180,6 +196,7 @@ impl CoreProcessHandle {
                     };
 
                     apply_core_color_env(&mut cmd);
+                    apply_core_no_window(&mut cmd);
                     let child = cmd
                         .spawn()
                         .map_err(|e| format!("failed to spawn core process: {e}"))?;

app/src-tauri/src/lib.rs

@@ -222,6 +222,13 @@ async fn run_core_cli(args: Vec<String>) -> Result<String, String> {
         }
         cmd.args(&args);
 
+        #[cfg(windows)]
+        {
+            use std::os::windows::process::CommandExt;
+            const CREATE_NO_WINDOW: u32 = 0x0800_0000;
+            cmd.creation_flags(CREATE_NO_WINDOW);
+        }
+
         log::info!(
             "[service-direct] running {:?} {}{}",
             bin,